Solid-state lighting arrays are used for a number of lighting applications. Solid-state light emitting devices used in such an array may include, for example, packaged light emitting devices including one or more light emitting diodes (LEDs). Such LEDs may include inorganic LEDs, which may include semiconductor layers forming p-n junctions and/or organic LEDs (OLEDs), which may include organic light emission layers.
Solid-state lighting panels including arrays of solid-state light emitting devices have been used as direct illumination sources, for example, in architectural and/or accent lighting. Solid-state lighting devices are also used in lighting fixtures, such as incandescent bulb replacement applications, task lighting, recessed light fixtures and the like. For example, Cree, Inc. produces a variety of recessed downlights, such as the LR-6 and CR-6, which use LEDs for illumination. Solid-state lighting panels are also commonly used as backlights for small liquid crystal display (LCD) screens, such as LCD display screens used in portable electronic devices, and for larger displays, such as LCD television displays.
Some attempts at providing solid-state lighting sources have involved driving an LED or string or group of LEDs using a rectified AC waveform. However, because the LEDs require a minimum forward voltage to turn on, the LEDs may turn on for only a part of the rectified AC waveform, which may result in visible flickering, may undesirably lower the power factor of the system, and/or may increase resistive loss in the system. Examples of techniques for driving LEDs with a rectified AC waveform are described in U.S. Patent Application Publication No. 2010/0308738, U.S. Patent Application Publication No. 2010/0231133, and in copending U.S. patent application Ser. No. 12/777,842, filed May 7, 2010), the last of which is commonly assigned to the assignee of the present application. Other control techniques for AC-powered solid state lighting apparatus are described in U.S. patent Ser. No. 13/235,103 entitled “Solid State Lighting Apparatus and Methods Using Energy Storage”, filed Sep. 16, 2011, and U.S. patent Ser. No. 13/235,127 entitled “Solid State Lighting Apparatus and Methods Using Current Diversion Controlled by Lighting Device Bias States”, filed Sep. 16, 2011.